Mail Sorters Are Harmful for Workers, Study Finds

Automatic mail sorting machines used in U.S. Postal Service centers across the country pose a serious health risk, forcing workers to engage in awkward, repetitive movements that can inflict serious back and arm problems, according to a government investigation.

Work at the machines “is potentially hazardous to employees due to design flaws and the high volume capacities of these machines,” says a report by the National Institute for Occupational Safety and Health.

A copy of the report, which was sent to postal authorities in Denver last Thursday, was obtained by The Times.

The Postal Service refused to comment on the study. “I haven’t seen a copy of the report yet,” said Dr. Rose Hayes, the Postal Service specialist in ergonomics, which is the study of equipment and its impact on the health of workers.

Workers in the Denver mail-processing center asked for the investigation by the institute, which is a branch of the federal Department of Health and Human Services. Ergonomic experts studied videotapes taken by investigators showing postal workers using the equipment at major mail-processing centers in Merrifield, Va., in August, and Denver in December.

The equipment is at the heart of the Postal Service’s continuing automation program, which emphasizes equipment that can read addresses and speed the sorting and delivery of mail.

The machines are called optical character readers, bar code sorters and delivery bar code sorters. By 1995, the Postal Service will have more than 9,000 of the machines installed at major centers across the country. They are used by three shifts of workers, 24 hours a day.

Government investigators found serious problems with two of the three types of machinery--optical character readers and delivery bar code sorters--that could put at potential risk the health of many thousands of workers.

The optical character readers scan ZIP codes and addresses printed on mail, then rapidly sort it by destination. Workers who feed mail to the machine are at risk of low back problems because they stoop and bend to pick up trays of mail from rolling carts and then bend again to place the mail on the feeding table, which is lower than the “recommended work surface height,” the report notes.

The delivery bar code sorter, which reads bar codes on mail, sorts the mail into slots called stackers. Workers using a tool called a pinch-grip take the mail and transfer it into trays for distribution. The machine has three levels of stackers. The lowest is 21 inches high and the top level is 50 inches off the floor. “These tasks place the shoulders, lower forearms and hands at risk for musculoskeletal disorders,” according to the report.

“A short worker would be best able to reach to the bottom tier but would have difficulty reaching the top tier,” according to the report. “A tall worker could more easily reach the top tier but would have to bend excessively to sweep mail from the bottom tier.”

“The current design, 102 stackers arranged in three rows with no adjustable features, results in excessive flexion of the trunk and shoulders for all employees,” the report said. Those movements “can lead to low back and upper extremity musculoskeletal disorders.”

Times researcher Ann Rovin in Denver contributed to this story.